Which one of the following keystrokes or characters is sent as p

Which one of the following keystrokes or characters is sent as part of ARQ communications to end the radio link?

A.Four “N”s. i.e. “NNNN”.

B.“BRK+”.

C.Four “K”s. i.e. “KKKK”.

D.Five periods (“…..”)

正确答案是B